Chris Watts‘s appearance on Denver7 will be key evidence against him in the alleged murders of his wife and their two daughters, say Law&Crime founder Dan Abrams and former prosecutor Nancy Grace.

The defendant appeared for an on-camera interview with the outlet when his spouse Shanann, four-year-old child Bella, and 3-year-old child Celeste were simply considered missing. He claimed he didn’t know their whereabouts, and claimed that his wife said she was going to a friend’s house with the kids. But Denver7’s Tomas Hoppough told ABC News that Watts seemed very calm amid the interview.

“He talked to me about basketball, about North Carolina basketball, before everything,” Hoppough said.

According to the arrest affidavit, Watts ended up telling police that he killed his wife Shanann, but only after she strangled their daughters.

Abrams said that this Denver7 interview will show that Watts was lying.

“Even if you take his version of the facts, he knew she was dead,” Abrams said. “He knew his kids were dead, and he’s pretending as if, ‘Oh, I just want you to come back.’ That’s going to be devastating.”

Then Grace said something perhaps never better uttered in her debates with Abrams: “Dan, you are so right about that.”

Grace added, “They’re going play that in front of the jury. In addition to that, when you are supposed to be determining his credibility, which is the sole province of a jury, and you’ve got him right there lying, according to his own statement later about what happened, how could they believe what his attorneys say at trial? They’ve already got him on video lying.”

Grace and Abrams also agreed that it was irrelevant that a witness saw Watts appear detached from his family during a vacation a couple of weeks before.

“It doesn’t mean a hill of beans,” Grace said. “I mean look at your own family photos. The men are always standing looking off in the other direction.”

Grace and Abrams did disagree about the relevance of a YouTube video by Watts from 2012. In it, he discusses the ways a relationship can fall apart, even bringing up the possibility of developing feelings for a co-worker. Watts suggests that a child could help repair a marriage. The footage is certainly evocative. The defendant told police he demanded a separation from Shanann (who was 15-weeks pregnant), and cops determined he had been in an affair with a co-worker, according to the affidavit. But will a court consider the footage relevant to the case as evidence?

Abrams said no. The mere fact that Watts discusses marital issues isn’t relevant, and won’t be brought in as evidence.

Nancy argued that it will help establish motive for the alleged murders, though she acknowledged there’s a “time problem” because the footage came from six years before the case. The jury can figure out if the video is relevant, she said.